Steering column with non-compliant torque sensor

ABSTRACT

An electric power steering system for a vehicle comprising a hand wheel in operable communication with a shaft, a motor in mechanical communication with the shaft, and a non-compliant torque sensor located between about a midpoint along the shaft and an upper end of the shaft.

BACKGROUND

[0001] In a typical electric power steering (EPS) system, a hand wheelis connected to a shaft, which comprises an upper shaft and a lowershaft connected by a torsion bar. The upper shaft connects to the handwheel and the lower shaft connects to an intermediate shaft thatultimately connects to the rack and pinion gear of a vehicle. When thehand wheel is turned, the upper shaft rotates and a torque sensormeasures the angular displacement of the torsion bar. The torque sensoris typically located at the interface between the upper and the lowershaft, which is also the location of the torsion bar. The type of torquesensor typically used has been a contacting type, which requires use ofa torsion bar to measure the amount of twist on the torsion bar. Thetorque sensor sends a signal to the controller, which then sends asignal to the motor to begin operating. The motor powers a gearmechanism, which provides assistance in turning the lower shaft andultimately the road wheels.

SUMMARY

[0002] An electric power steering system for a vehicle comprising a handwheel in operable communication with a shaft, a motor in mechanicalcommunication with the shaft, and a non-compliant torque sensor locatedat the shaft between about a midpoint along the shaft and an upper endof the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Referring now to the drawings wherein like elements are numberedalike in the several Figures:

[0004]FIG. 1 is a schematic perspective view of a steering system of avehicle;

[0005]FIG. 2 is a top view of an EPS system with a motor;

[0006]FIG. 3 is a cross-section view of an EPS system with a singleshaft and single housing unit;

[0007]FIG. 4 is a cross-section view of an alternative embodiment EPSsystem with a single shaft, a bracket/jacket housing unit, andinstallation brackets;

[0008]FIG. 5 is a cross-section view of an alternative embodiment EPSsystem with a single shaft, a bracket/jacket housing unit, installationbrackets, and an additional bearing;

[0009]FIG. 6 is a cross-section view of an alternative embodiment EPSsystem with a single shaft, a bracket/jacket housing unit, installationbrackets, additional bearings, and a controller that is separated fromthe non-compliant torque sensor;

[0010]FIG. 7 is a cross-section view of an alternative embodiment EPSsystem with an upper shaft, a lower shaft, a torsion bar, anon-compliant torque sensor, and a controller;

[0011]FIG. 8 is a cross-section view of an alternative embodiment EPSsystem with an upper shaft, a lower shaft, a torsion bar, and anon-compliant torque sensor;

[0012]FIG. 9 is a cross-section view of an alternative embodiment EPSsystem with an upper shaft, a lower shaft, a torsion bar, a joint, anon-compliant torque sensor, and a controller;

[0013]FIG. 10 is a cross-section view of an alternative embodiment EPSsystem with an upper shaft, a lower shaft, a controller, and anon-compliant torque sensor; and

[0014]FIG. 11 is schematic perspective view of a non-compliant torquesensor.

DETAILED DESCRIPTION

[0015] Referring to FIG. 1, the steering system 20 comprises an EPSsystem, which is connected at a hand wheel 24 through a shaft 26 and ahousing 28. The EPS system provides a driver with assistance in turninga vehicle's road wheels 22. The driver turns the hand wheel 24, which ismechanically connected to a shaft 26. The rotational force of the handwheel 24 is transmitted to the shaft 26, which is detected by anon-compliant torque sensor 30. The non-compliant torque sensor 30 islocated at the shaft 26 from about a midpoint 29 at the shaft 26 to anupper end 27 of the shaft 26. The non-compliant torque sensor 30measures the torque applied to the shaft 26 and sends a signal to acontroller 38, which may be a column electronics module. The controller38 then sends a signal to the motor 32 to begin operation. The motor 32,which is in mechanical communication with a worm 34 and a worm gear 36,rotates the worm 34 and the worm gear 36, which provide turningassistance to the shaft 26. As the shaft 26 turns, an intermediate shaft33, connected through a universal joint 31 rotates a pinion gear (notshown) located under a gear housing 35. Rotation of the pinion gear (notshown) moves a rack 29, which moves a tie rod 37. When the tie rod 37moves, it turns a steering knuckle 39, which turns a road wheel 22.

[0016] Referring to FIGS. 2 and 3, the EPS system and shaft 26 aremounted to a vehicle by a housing 28, which may be a single cast unit.The EPS system, shaft 26, and housing 28 collectively may be referred toas the steering column 60. Referring to FIG. 3, an upper bearing 44 anda bearing 46 support the shaft 26. The upper bearing 44 is secured tothe shaft 26 by a retaining ring 42. A bearing lash eliminator 48 ispressed between the upper bearing 44 and the retaining ring 42.

[0017] A position sensor 70, which detects the position of the handwheel (not shown), is connected to a bracket switch mounting 68, whichis in operable communication with the controller 38. The bracket switchmounting 68 is mounted to the face of the housing 28. Both the positionsensor 70 and the bracket switch mounting 68 are located adjacent to thehand wheel (not shown).

[0018] As stated above, the non-compliant torque sensor 30 is locatedanywhere from about a midpoint 29 at the shaft 26 to an upper end 27 ofthe shaft 26. A spacer 50 may be used to locate the non-compliant torquesensor 30 on the shaft 26 in proximity to the end of the controller 38.The non-compliant torque sensor 30 comprises a magnetometer housing 52,which is secured to a bearing housing 54 by a fastener 56. The bearinghousing 54 contains a bearing 58 and a bushing 64, which supports themagnetometer housing 52 and secures it to the shaft 26. A snap ring 62secures the bearing housing 54 to the shaft 26. Preferably, there is aconnection pathway 66 in the housing 28 to directly connect thenon-compliant torque sensor 30 to the controller 38, which is located onthe face of the housing 28 adjacent to the hand wheel (not shown).

[0019] Referring to FIG. 11, the non-compliant torque sensor 30comprises a transducer 202 and a magnetic field vector sensor 204. Thetransducer 202 comprises one or more axially distinct, magneticallycontiguous, oppositely polarized circumferential bands or regions 206,208 solely defining the active or transducer region of the shaft 26.Region 210 of the shaft to the left of A and region 212 to the right ofB are distinguishable from the active region only by the absence of anysignificant remanent magnetization. The shaft 26 is typically formed ofa ferromagnetic, magnetostrictive material having a particularlydesirable crystalline structure. Torque 214 is applied at one portion ofthe shaft 26 and is transmitted thereby to another portion of the shaft26 where the motion of the shaft 26 due to torque 214 ultimately turnsthe road wheels (not shown) of the vehicle. Torque 214 is being shown asbeing in a clockwise direction looking at the visible end of the shaft26, but obviously can be applied to rotate in either direction dependingon the direction the driver turns the hand wheel (not shown).

[0020] A magnetic field vector sensor 204 is a magnetic field vectorsensing device located and oriented relative to the transducer 202 so asto sense the magnitude and polarity of the field arising in the spaceabout the transducer 202 as a result of the reorientation of thepolarized magnetization from the quiescent circumferential direction toa more or less steep helical direction. The magnetic field vector sensor204 provides a signal output reflecting the magnitude of torque 214 andelectrically connected to the controller (not shown). The non-complianttorque sensor 30 is more fully described in U.S. Pat. No. 6,145,387,which is incorporated in its entirety herein by reference.

[0021] Referring to FIGS. 2 and 3, when the controller 38 receives asignal from the non-compliant torque sensor 30, the controller 38 thensends a signal to the motor 32 to turn on. When the motor 32 turns on itturns the shaft 26 through a worm 34 and worm gear 36 assembly. The worm34 is rigidly connected to a motor 32 and mounted to a worm gear 36. Aworm gear 36 is mounted to the shaft 26 on splines (not shown). A spring74 is mounted between the splines (not shown). A nut 72 supports theworm gear 36 in place along the shaft 26. A bearing 46 supports the wormgear 36 at the shaft 26.

[0022] Referring to FIG. 2, a magnetorheological fluid stopper 40 ismounted on the motor 32. The magnetorheological fluid stopper 40 isfully described in U.S. application Ser. No. 09/825,793, filed Apr. 4,2001 entitled, “Magnetorheological Fluid Stopper At Electric Motor”under Attorney docket number DE3-0215 and client docket numberDP-303759, which is incorporated in its entirety herein by reference.

[0023]FIG. 4 shows an alternative embodiment of the steering column 60.This embodiment has many of the same components as the embodiment inFIG. 3, like elements being numbered alike. Distinctions are discussedhereunder. The housing 400 comprises a bracket 401 and jacket 402secured to each other, which may be by welding shown as a weld bead 404.The housing 400 is mounted to the vehicle (not shown) by an upperinstallation bracket 406 and a lower installation bracket 408. The lowerinstallation bracket 408 is attached to the shaft 26 by a bolt 414. Inthis embodiment, the worm gear 36 is supported by a bearing 410, whichis pressed onto the shaft 26 and into a bearing recess 411. Moreover,the worm 34 and the worm gear 36 are housed in a worm gear housing 412.Referring to FIG. 5, this embodiment is similar to the embodimentdescribed in FIG. 4, except the worm gear 36 is supported by bearings502, 504, which are pressed onto the shaft 26 into bearing recesses 506,508 on either side of the worm gear 36.

[0024] Referring to FIG. 6, an alternative embodiment is disclosed. Thisembodiment is similar to the one disclosed in FIG. 4, like elementsbeing numbered alike. The non-compliant torque sensor 30 is not directlyconnected to the controller 38. Instead, a plug 67 provides theconnection from the non-compliant torque sensor 30 to a harness (notshown) and subsequently to the controller 38. The worm gear 36 issupported by two bearings 602, 604, which is pressed onto the shaft 26into bearing recesses 610, 612 and located to one side of the worm gear36. A larger worm gear housing 606 is shown, along with a differentupper installation bracket 608.

[0025]FIG. 7 discloses an alternative embodiment. The driver turns ahand wheel (not shown), which is operably connected to an upper shaft702. The upper shaft 702 is connected to a lower shaft 704 through atorsion bar 706, which is supported by a needle bearing 718. Anon-compliant torque sensor 30, which is secured to an upper shaft 702,measures the torque and sends a signal to a controller 38. Thecontroller 38 may be a column electronics module. The non-complianttorque sensor 30 is secured to the upper shaft 702 in the same method aswas disclosed in FIG. 3. The non-compliant torque sensor 30 is locatedat the upper shaft 702 and may be located anywhere along the upper shaft702, which may be between an upper end 703 of the upper shaft 702 and aconnection 705 of the upper shaft 702 and the torsion bar 706. Thespacer 50 may be used to locate the non-compliant torque sensor 30 onthe upper shaft 702 in proximity to the end of the controller 38. Thenon-compliant torque sensor 30 is directly connected to the controller38 through a connection pathway 66 in a housing 400. In addition, aposition sensor 70 and a bracket switch mounting 68 are the same as wasdisclosed in FIG. 3. Once the controller 38 receives a signal from thenon-compliant torque sensor 30, it then sends a signal to a motor (notshown) to turn on. When the motor (not shown) activates, it rotates thelower shaft 704 through a worm 34 and a worm gear 36 assembly. The worm34 is connected to a motor 32 and mounted to a worm gear 36. A worm gear36 is mounted to the lower shaft 704. The worm 34 and the worm gear 36are housed in a worm gear housing 412. A nut 710 presses a bearing 714to the worm gear housing 412 along the lower shaft 704. The lower shaft704 is connected to an intermediate shaft 33 through a universal joint31.

[0026] The housing 400 for the steering column 60 comprises a bracket401 and jacket 402 fixably attached to each other, which may be bywelding shown as a weld bead 404. The housing 400 is mounted to thevehicle (not shown) by an upper installation bracket 406 and a lowerinstallation bracket 408. Two bearings 714, 716, which are pressed ontothe lower shaft 704 and into bearing recesses 720, 722, support the wormgear 36 at the lower shaft 704. The lower installation bracket 408 isattached to the lower shaft 704 by a bolt 414.

[0027] Referring to FIG. 8, an alternative embodiment is disclosed. Theembodiment is similar to the one disclosed in FIG. 7, like elementsbeing numbered alike. The controller 38 is attached to the worm gearhousing 412. As such, the non-compliant torque sensor 30 is not directlyconnected to the controller 38. A plug 67 located on the non-complianttorque sensor 30 provides the connection from the non-compliant torquesensor 30 to the controller 38. The position sensor 70 is also locatedon the other side of the non-compliant torque sensor 30 and is betweenthe non-compliant torque sensor 30 and the worm gear housing 412. Theposition sensor is operatively connected to the upper shaft 702.Moreover, there is no spacer locating the non-compliant torque sensor 30along the upper shaft 702.

[0028] Referring to FIG. 9, an alternative embodiment is disclosed. Theembodiment is similar to the one disclosed in FIG. 7, like elementsbeing numbered alike. The upper shaft 702 is operably connected to aspool shaft 902 through a joint 904 to permit angular adjustments. Thereare two bearings 906, 908, which are pressed onto the lower shaft 704and into bearing recesses 914, 916 and support the lower shaft 702 andthe worm gear 36 along the lower shaft 702. The non-compliant torquesensor 30 is not directly connected to the controller 38; rather a plug67 is provided for the electrical connection. Moreover, the worm gearhousing 910 is bigger and a different upper installation bracket 912 isutilized to mount the housing 400 to the vehicle (not shown).

[0029] Referring to FIG. 10 an alternative embodiment is disclosed. Theembodiment is similar to the one disclosed in FIG. 9, with the exceptionof the following parts. The controller 38 is attached to the worm gearhousing 412. As such, the non-compliant torque sensor 30 is not directlyconnected to the controller 38. A plug 67 located at the non-complianttorque sensor 30 provides the connection from the non-compliant torquesensor 30 to the controller 38. The position sensor 70 is also locatedon the other side of the non-compliant torque sensor 30 and is betweenthe non-compliant torque sensor 30 and the worm gear housing 412.Moreover, the worm gear housing is similar to the one disclosed in FIG.7 and there is no spacer locating the non-compliant torque sensor 30along the upper shaft 702.

[0030] It will be understood that a person skilled in the art may makemodifications to the preferred embodiment shown herein within the scopeand intent of the claims. While the present invention has been describedas carried out in a specific embodiment thereof, it is not intended tobe limited thereby but is intended to cover the invention broadly withinthe scope and spirit of the claims.

What is claimed is:
 1. An electric power steering system for a vehiclecomprising: a hand wheel in operable communication with a shaft; a motorin mechanical communication with said shaft; and a non-compliant torquesensor located at said shaft and located between about a midpoint alongsaid shaft and an upper end of said shaft.
 2. The electric powersteering system in claim 1 wherein said shaft comprises a single shaft.3. The electric power steering system in claim 1 further comprising asingle cast housing.
 4. A steering column for a vehicle comprising: ashaft controlled by a hand wheel; a gear assembly in mechanicalcommunication with said shaft; a motor in mechanical communication withsaid gear assembly; a controller in operable communication with saidmotor; a non-compliant torque sensor located at said shaft and locatedbetween about a midpoint along said shaft and an upper end of saidshaft; and a position sensor in electronic communication with saidcontroller and connected to a bracket switch mounting.
 5. The steeringcolumn in claim 4 wherein said shaft comprising a single shaft.
 6. Thesteering column in claim 4 wherein said gear assembly comprises a wormand a worm gear.
 7. The steering column in claim 4 further comprises asingle cast housing.
 8. The steering column in claim 4 comprises ahousing wherein a bracket connects to a jacket.
 9. The steering columnin claim 7 wherein said controller is mounted on a face of said housingadjacent to said hand wheel.
 10. The steering column in claim 7 whereinsaid non-compliant torque sensor is directly connected to saidcontroller through a connection pathway in said housing.
 11. Thesteering column in claim 4 wherein said non-compliant torque sensor isconnected to said controller through a plug.
 12. The steering column inclaim 4 wherein said controller is a column electronics module.
 13. Asteering column for a vehicle comprising: an upper shaft controlled by ahand wheel; a lower shaft connected to said upper shaft by a torsionbar; a gear assembly in mechanical communication with said lower shaft;a motor in mechanical communication with said gear assembly; acontroller in electronic communication with said motor; a non-complianttorque sensor located at said upper shaft between said connection ofsaid upper shaft and said torsion bar and an upper end of said uppershaft; and a position sensor in electronic communication with saidcontroller.
 14. The steering column in claim 13 wherein said gearassembly comprises a worm and a worm gear.
 15. The steering column inclaim 13 wherein said worm and said worm gear are housed in a worm gearhousing.
 16. The steering column in claim 13 further comprising ahousing wherein a bracket connects to a jacket.
 17. The steering columnin claim 16 wherein said controller is mounted at a face of said housingadjacent to said hand wheel.
 18. The steering column in claim 13 whereinsaid non-compliant torque sensor is directly connected to saidcontroller through a connection pathway in said housing.
 19. Thesteering column in claim 13 wherein said non-compliant torque sensor isconnected to said controller by a plug.
 20. The steering column in claim13 wherein said controller is a column electronics module.